I had my first run/brick-brick session of the year last night. R-B-R-B-R with biking on my turbo trainer thingy. That followed a (deliberately) slow parkrun on Saturday, where I was practicing my running form, trying to get my shoulders level, arm swing, and foot strike right. Anyway, that slow 5k killed my calves and hurt my shoulders!
Not an auspicious start to the notorioulsy painful brick sessions.
With the brick on Sunday I took it slowly trying to approximate my run and ride paces/speeds to something approximating a sweetspot pace. So just shy of 160 HR (my lactate is HR 173/4/5 and my HRmax 193 to give you an idea). So you still sweat but you certainly wouldn’t class the effort as hard even though I did it for over an hour. The first transition back to the bike from the first run felt not very nice at all and it took a good 10 minutes for my legs to get properly going. I was doing high cadences of around 100 so high enough to try to flush out those nasty lactates/H+ ions.
And after, with the subsequent bike/run changes, it all went quite well really thank you very much. Next Sunday’s will be harder of course. But I achieved the goal of reminding myself what duathlon is all about much to the chagrin of my legs!
Still the run parts felt quite tough – especially considering as I was only averaging 4min/km over about 1 mile. Indeed that is what this post is moaning about. My 5k times have taken quite a knock over the winter as I’ve built up the mileage and introduced swimming into my regime. I had done a few speed sessions and so was hoping to approach the spring where I left off in October, but it is not to be. It is now time to really get my legs going.
But not today it isn’t as it’s already a rest day! (I think I’ll go swimming). Hmmm maybe that’s why the 5k times are down.
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Last Updated on 13 December 2025 by the5krunner
tfk is the founder and author of the5krunner, an independent endurance sports technology publication. With 20 years of hands-on testing of GPS watches and wearables, and competing in triathlons at an international age-group level, tfk provides in-depth expert analysis of fitness technology for serious athletes and endurance sport competitors.
This sounds familiar! My 5k focus has suffered hugely since the end of the summer/early autumn since I switched to focusing on endurance and prep for my first duathlon. I love the pool so that”s always a distraction and I’ve upped my conditioning work too. Did some brick training today but part of me wants the duathlon over so I can get back to some pure running training. 😀